System and method for filling joints between exterior cement panels

ABSTRACT

Buildings and walls are commonly constructed with exterior walls composed of fiber exterior panels, such as fiber cement panels or glass reinforced gypsum exterior sheeting. The spaces between the exterior panels are sealed using the system and method of the present invention. The space is first filled with an acrylic flexible joint compound. A thermally set, spunbonded, reinforced, polyester non-woven joint tape is then applied. The tape is then covered with a ceramic mud. After curing of the ceramic mud an acrylic elastomeric coating is sprayed, brushed or rolled on the fiber cement panels. A cement-free stucco coating or a variety of other coatings may then be applied over the exterior panels.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 60/635,598, filed Dec. 13, 2004, the disclosure of which is incorporated by reference as if fully set forth herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Federally Sponsored Research or Development was not used in the invention.

FIELD

The present invention relates to an improved system and method for sealing the spaces between exterior cement panels fastened to building frames to allow for the application of paint, a synthetic stucco finish or other covering on the exterior cement panels.

BACKGROUND

Stucco finishes are an example of an exterior finish that has been used on buildings since ancient times. Still widely used throughout the world, stucco exterior finishes make up one of the most common ways of finishing exteriors of both residences and commercial buildings.

Like interior wall plaster, a stucco finish has traditionally been applied on exterior surfaces as a multiple-layer process, sometimes consisting of one, two, but more commonly as three coats. Whether applied directly to a masonry substrate or onto wood or metal lath, the process of applying a stucco finish includes the step of applying a first “scratch” or “pricking-up” coat, followed by a second scratch coat, sometimes referred to as a “floating” or “brown” coat, followed finally by the “finishing” coat, Up until the late-nineteenth century, the first and the second coats were of much the same composition, generally consisting of lime or portland cement, sand, perhaps clay and one or more other natural additives. Straw or animal hair was usually added to the first coat as a binder.

The third, or finishing coat, consisted primarily of a very fine mesh grade of lime and sand, and sometimes pigment.

Although traditional stucco exterior finishes have been used for quite some time, traditional stucco exterior finishes have their limitations. Those limitations include porosity, rigidity, freeze/thaw fractures, fungal and mildew formation, cracking, complexity of installation, high maintenance and the requirement for a specialized labor pool to apply the stucco exterior finish.

Because modern synthetic stucco exterior finishes are watertight, any water that remains trapped behind these modern synthetic stucco exterior finishes does not readily evaporate. The trapped water behind the stucco exterior finish can then soak into the substrata and framing of the building. The water that soaks into the substrata and framing often causes severe damage to the building without any signs of damage appearing on the exterior of the building. These problems can exist regardless of the age of the building or the quality of construction. Another problem leading to severe damage is insulation cladding. Specifically, insulation cladding is unforgiving for water penetration or condensation. Moreover, the durability of the cladding itself is prone to penetration by abrasion, birds, insects and airborne debris.

Although modern synthetic stucco exterior finishes are attractive and long lasting, their usefulness is compromised by the integrity of the foundation to which it is applied. It has been found that one of the most durable foundations for a synthetic stucco exterior finishes uses fiber cement panels affixed to the building frame.

The recent introduction of a fiber-cement panel available in 4×8, 9 and 10 ft lengths and in ¼ and 5/16^(th) inch widths, has provided an opportunity to replace prior art systems with a preformed fiber cement panel that can be installed like wood paneling or interior drywall panels. However, just like interior drywall panels, exterior fiber cement panels, when installed, have seams or joints between each panel that must be filled so that a smooth exterior finish may be applied there over.

To create a pleasing and uniform appearance for the exterior of a building, the outline of each exterior fiber cement panel should be invisible. For interior drywall panels, hiding the outline of each drywall panel is achieved by tapering the edges of the individual panels so that when the drywall panels abut one another, the tapered edges provided a channel suitable for the use of tape and mud to hide the resulting seams. The process of taping and placing mud over the tape creates a smooth transition between drywall panels. Unfortunately, unlike interior drywall panels with their tapered edges, exterior fiber cement panels do not have tapered edges and do not form a channel which is easily filled and masked. Hence, when exterior fiber cement panels are placed along side each other on the exterior of a building, a butt-joint with square edges is created. The butt-joint between the exterior fiber cement panels is difficult to disguise. In addition, the edges of each exterior fiber cement panel are subject to the stresses of building movement, temperature changes and other environmental factors. Accordingly, the foregoing factors must be considered when finishing an exterior wall so that no seams or joints between exterior wall panels are visible.

One prior art solution teaches simply filling the gaps between exterior fiber cement panels with a polyurethane caulk. The polyurethane caulk is then covered with a 3-inch wide, peal and stick butyl-rubber tape having a fabric backing. This butyl-rubber tape and the rest of the panel is then coated with an exterior synthetic stucco finish coat. This solution has proven to be unsatisfactory because it overlooks the problems of out-gassing from the polyurethane caulk. Specifically, if the caulk isn't fully cured due to time or climate constraints and is then covered by a non-permeable butyl rubber tape, the emission of gas from the polyurethane caulk causes blisters or ridges to form in the butyl-rubber tape as the trapped gas tries to escape (out gas) from the polyurethane caulk. In addition, there is also a tendency for the butyl-rubber tape to show noticeable bumps if any air becomes trapped while handling and applying the butyl-rubber tape to the panel. Furthermore, the butyl-rubber tape is extremely tacky and by its very nature, may bulge outwardly from the butt-joint between the exterior fiber cement panels when the tape is smoothed flat against the surface of the exterior fiber cement panel.

The prior art approach of placing butyl-rubber tape over a polyurethane caulk overlooks the problem presented by a butt-joint between exterior fiber cement panels. By sealing the polyurethane caulk with a butyl-rubber tape, an elevation is created at the seams between the exterior fiber cement panels. This elevation accentuates the outline of the panels. Flexibility at the butt-joint between the exterior fiber cement panels is then compromised. To address the problem of accentuating rather than hiding panel outlines, applicators have attempted to place multiple layers of a stucco exterior finish over the exterior fiber cement panels. These multiple layers of stucco increase the material and labor cost. Moreover, any irregularities still evident after the stucco exterior finish is applied will be very difficult, if not impossible, to hide. Lastly, the use of a butyl-rubber tape over a polyurethane caulk also overlooks the benefits of a weep screed, thereby compromising drainage of any moisture penetration.

Accordingly, there still remains a need in the art for a system and method for filling the space between exterior panels, that provides a smooth appearance for painting or the application of an exterior finish such as stucco, paint, or other commonly used finish.

SUMMARY

The system and method of the present invention provides for filling the space between exterior panels, such as fiber cement panels, to provide a smooth appearance suitable for painting, the application of a stucco or an other finish which will last for the life of the building onto which the exterior panels are attached.

First, an acrylic flexible joint compound is layered into and over the space between the fiber cement panels. Next, a thermally set, spunbonded polyester nonwoven reinforced joint tape is placed over the space filled by the acrylic flexible joint compound. Following the application of the thermally set spunbonded polyester nonwoven joint tape a ceramic mud is applied. Following the application of the ceramic mud a colored acrylic elastomer coating can be applied over the ceramic mud and there entire wall assembly. Paint or stucco or other finish may then be applied over the colored base.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the system and method for filling joints between exterior panels may be had by reference to the drawing figure, wherein:

FIG. 1 is a perspective of an exterior wall illustrating the system and method of the disclosed invention;

DETAILED DESCRIPTION OF THE EMBODIMENTS

This present invention describes an improved system and method for preparing and finishing exterior panels or other cement board formats with cement free, exterior textured wall coatings and finishes.

The invention as shown in FIG. 1 involves a hybrid application process that prepares exterior panels, such as fiber-cement panels, or glass reinforced gypsum exterior sheeting like interior gypsum drywall for the purpose of creating a smooth exterior stucco or painted finish. Exterior fiber-cement panels are first secured to the building frame per manufacturer's guidelines. The spaces between the panels are then filled and effectively made to disappear by use of the disclosed system and method.

This disclosed system and method enables the creation of stucco like finishes, over fiber cement panel walls, with greater strengths and benefits not present in typical stucco or prior art exterior insulation finish systems. This disclosed system and method may be best understood by those of ordinary skill in the art as a tape and float system that integrates the skills, techniques and materials from heretofore unrelated areas to create a smooth base for stucco-like finishes and textures.

Like drywall, fiber-cement wall panels are installed on an exterior building frame with the adjacent edges of the panels butted together. An optional weep screed termination at the base of the panel provides a level line, a drainage plane and corner bead like protection. In the preferred embodiment of the invention, once the fiber cement panels are mounted to the building frame, an acrylic flexible joint compound such as sold under the trademark AcraCream® by Global Coatings, Inc. is applied with a 6-inch joint knife over the center of the butt-joint. In the preferred embodiment 4-inch, thermally set, spunbonded polyester reinforced nonwoven joint tape, is laid into the acrylic flexible joint compound and embedded into the acrylic flexible joint compound with the aid of the joint knife. Those of ordinary skill in the art will understand that other types of take having similar properties such as fiberglass tape may be used without departing from the scope of the disclosed invention. Heretofore, the thermally set, spunbonded polyester nonwoven reinforced joint tape used with the system and method of the present invention had been used primarily in the manufacture of furniture and commercial roof seam sealing. Once cured, the acrylic flexible joint compound shrinks into any gap, then fills and seals the spaces between the fiber cement panels. The acrylic flexible joint compound may also be used on metal or plastic corner beads to build them out to be flat and smooth. The thermally set spunbonded, reinforced polyester non-woven joint tape, is embedded into the acrylic flexible joint compound. It has been found that the thermally set spunbonded, reinforced polyester non-woven reinforced joint tape provides added stability and flexibility to the cured acrylic flexible joint compound. The preferred AcraCream® joint compound is a mixture by weight of Acrylic Polymer 54%, Calcium Carbonate 30%, Water 5%, isobutane 4%, titanium dioxide 2% and petroleum derivatives 2%.

Together, the acrylic flexible joint compound and the thermally set spunbonded, reinforced polyester non-woven reinforced joint tape, both seal and waterproof the butt-joint with a rubber gasket-like membrane. This tough rubber gasket-like membrane accommodates and flexes along with the exterior building panels. Moreover, the remaining profile of the butt-joint is minimal, and the rubber gasket-like membrane provides an acrylic adhesive bedding for the use of the ceramic mud that follows.

Once the thermally set spunbonded, reinforced, polyester, non-woven reinforced joint tape has been smoothed over the acrylic flexible joint compound, a ceramic mud is applied. It has been found that a ceramic mud sold under the trademark Fill-N-Build® by Global Coatings, Inc. provides satisfactory results. Heretofore Fill-N-Build ceramic mud had only found utilization for filling the spaces under interior hardwood floors. Fill-N-Build ceramic mud is a mixture by weight of Acrylic copolymer solution 30%, hydrated aluminum silicate mineral 19.5%, soda lime borosilicate glass 10%, kaolin clay 8%, Titanium dioxide 4%, and ammonium salt of acrylic polymer 1%. As with interior drywall that has been installed without a tapered edge, the exterior fiber cement panel needs to be floated out 10 or more inches on each side of the butt-joint. This floating and feathering of the butt-joint between the exterior fiber cement panels, helps flatten and level the exterior wall so that the spaces between the panels are no longer noticeable. Like interior drywall mud, the ceramic mud may also be applied over all nail heads. It has been found, those using the system and method of the present invention that if the acrylic flexible joint compound can be made to be extremely smooth only a small amount, if any, ceramic need be used.

Unlike the mud used with interior drywall the ceramic mud used in the system and method of the present invention is a gypsum-free, ceramic-acrylic-clay matrix that, once cured, does not dissolve or deteriorate when exposed to exterior weather. The ceramic mud is applied over the tape using a 10 or 12-inch mud knife and then floated 10-12 inches on each side of the thermally set, spun bonded, reinforced polyester non-woven joint tape over the butt-joint creating a total width of 20-24 inches of ceramic mud over the butt-joint between the fiber cement panels. Care must be taken not to apply much ceramic mud over the center of the butt-joint but rather to float the ceramic mud away from the butt-joint to create a seamless and flat transition between the exterior fiber cement panels.

The ceramic mud may also be used to treat metal or plastic corner beads, building them out until the corner beads are flat and smooth with the exterior fiber cement panel. Another major benefit of the system and method of the present invention is the capability of straightening the appearance of a wall that has been compromised by irregular studs. The ceramic mud can mask most any irregularity in the wall surface. As the ceramic mud is formulated with acrylic mastic, it provides a strong bond and cures with the underlying acrylic flexible joint compound. When dry, the ceramic mud may be sanded if required, providing an extremely smooth, flat surface for the application of the acrylic elastomeric coating that follows.

An acrylic elastomeric coating is then applied over the entire exterior cement fiber panels, including the area over the butt-joint. The acrylic elastomeric coating may be tinted to be the same color as the textured exterior finish top-coat which is either spray-applied, rolled or brushed onto the exterior of the building. Some applicators have found that the acrylic stomoric coating, if applied well, can be a satisfactory exterior coating. In actual applications, it has been observed that the acrylic based flexible joint compound cures to a tough acrylic rubber-like substance, and the acrylic elastomeric coating cures to a softer acrylic rubber-like substance with excellent freeze/thaw properties. Hence, the colder it gets, the more elastomeric it becomes. It has been found that an acrylic elastomeric coating sold under the trademark ColorFlex® by Global Coatings, Inc. provides satisfactory results. ColorFlex is a mixture by weight of acrylic polymer 43%, calcium carbonate 36%, water 11% titanium dioxide 5%, and calcium carbonate 3%.

This system and method of the present invention creates a dual acrylic rubber gasket sandwich with a ceramic core. Specifically, the tougher acrylic based flexible joint compound absorbs the building stress and the acrylic high performance colored coating provides a secondary exterior crack bridging and color prime component. When complete, the fiber cement wall appears as a smooth surface with none of the spaces or space treatment visible.

In another embodiment of the system and method of the present invention is the capability to touch up any wall areas in which a smooth surface is not observed. Specifically, before the final synthetic exterior texture is applied, further application of the ceramic mud over the acrylic flexible joint compound is possible. Once the ceramic mud has been applied, the acrylic elastomeric coating is applied.

Those of ordinary skill in the art will understand that the acrylic elastomeric coating is an integral component of a 4-ply membrane that includes both the underlying ceramic mud and acrylic flexible joint compound. The first layer of the acrylic flexible joint compound forms a tough acrylic rubber-like substance that acts like a shock absorber and waterproof membrane between the wall panels. The second layer is the thermally set, spunbonded, reinforced polyester nonwoven reinforced joint tape. The third layer of ceramic mud provides a smooth seamless foundation that bridges the space between the fiber cement panels and fills or levels any irregularities in the fiber cement panels themselves. The last layer is the acrylic elastomeric coating which provides secondary crack bridging capabilities and also accommodates exterior freeze/thaw.

Various exterior textures can then be applied to the fiber cement panel building exterior depending on the aggregate mix and the application technique. If synthetic stucco is used, the synthetic stucco cures to a stone-like veneer providing added durability to the underlying fiber cement panels. Furthermore, the system and method of the present invention provides independent elastomeric properties in the underlying acrylic coating and the components in the acrylic flexible joint compound synergistically work together to provide greater system flexibility and durability.

While the system and method of the present invention has been disclosed according to its preferred and alternate embodiments, those of ordinary skill in the art will understand that other embodiments of the invention are possible based on the foregoing disclosure. For example, while the disclosed system and method has been described with regard to fiber-cement panels, those of ordinary skill in the art will understand its utility with other types of exterior such as fiberglass reinforced gypsum board. Such other embodiments shall be included with the scope and meaning of the appended claims. 

1. A method for sealing the spaces between panels on exterior walls comprising the steps of: filling the joint with an acrylic based flexible joint compound; taping over said acrylic based flexible joint compound with a reinforced spunbonded joint tape; applying a layer of a ceramic mud over said tape; covering the entire panel with an acrylic elastometric coating;
 2. The method as defined in claim 1 wherein the acrylic elastometric coating is tinted to a desired color.
 3. A method for repair of imperfections in exterior wall panels comprising steps of: filling the imperfection with an acrylic based flexible joint compound; smoothing the filled imperfection with a ceramic mud; applying layering an acrylic elastometric coating over said ceramic mud;
 4. A method for sealing the spaces between exterior panels used in the construction of exterior walls comprising the steps of: filling the space with acrylic flexible joint compound, covering the said acrylic flexible joint compound with thermally set, spunbonded polyester nonwoven reinforced joint tape; and applying an acrylic elastomeric coating.
 5. The system as defined in claim 4 wherein said acrylic elastomeric coating is tinted to a desired color.
 6. A wall constructed of a plurality exterior panels affixed to an internal frame in which the spaces between said exterior panels are filled and sealed by the method of claim
 4. 7. The wall as defined in claim 6 further including a cement free stucco exterior finish.
 8. A building comprising: a plurality of exterior panels affixed to the building, said exterior panels having spaces there between wherein: the spaces between said exterior panels are filled with an acrylic flexible joint compound over which is layered a thermally set, spunbonded polyester nonwoven reinforced joint tape which optionally may be covered with ceramic mud to which an acrylic elastomeric coating is added.
 9. The building as defined in claim 8 further including a cement free stucco exterior finish.
 10. A system for filling and sealing the spaces between fiber cement panels attached to a building frame comprising a dual acrylic rubber-like gasket sandwich with or without a ceramic core. 